Oil or gas burner with a cross-current blower having return flow means

ABSTRACT

AN OIL OR GAS BURNER HAS A CASING FORMED BY A LOWER CASING MEMBER AND A COVER PLATE FORMING AN ELONGATED CASING WITH ROUNDED ENDS.. A BLOWER ROTOR IS LOCATED IN AN OPENING IN ONE OF THE ENDS, THE CASING WALL ADJACENT THE OPENING FORMING A GUIDE PLATE AT THE INTAKE SIDE OF THE ROTOR. THE ANGLE BETWEEN THE TANGENT TO THE CASING WALL AT THE BEGINNING OF THE GUIDE PLATE AND THE TANGENT TO THE CASING WALL AT THE OTHER END OF THE ROUNDED END PORTION IS LESS THAN 90*, PREFERABLY 30*-60*. THERE IS PROVIDED AT THE OTHER SIDE OF THE ROTOR FROM THE GUIDE PLATE, WHERE THE ROTOR IS SLIGHTLY SPACED FROM THE LONGITUDINAL WALL OF THE CASING, A VORTEX BAFFLE-PLATE WHICH TAPERS IN CROSS-SECTION TOWARDS THE PERPHERY OF THE ROTOR, AND BETWEEN WHICH AND THE END PORTION OF THE LONGITUDINAL WALL ONE OR MORE PASSAGES ARE FORMED THROUGH WHICH SOME OF THE AIR FED BY THE ROTOR CAN BE RETURNED FROM THE PRESSURE-SIDE TO THE SUCTION-SIDE.

June 6, 1972 K. ZENKNER 3,667,893

OIL OR GAS BURNER WITH A CROSS-CURRENT BLOWER HAVING RETURN FLOW MEANS Filed April 1, 1968 5 Shasta-Shoot 1 h E k g I i Q/ i 99 g a a g 1 a v I I i 1: R 1 4;, I Hi R Q a o g a a a 9g l i lb) 1 & L: Y\

l/ d 4| LL INVENTOR KURT ZENKUER ATTORNEY June 6, 1972 K. ZENKNER 3,667,893 on. on GAS BURNER WITH A CROSS-CURRENT BLOWER' HAVING RETURN FLOW MEANS 5 Shanta-Shut 2 Filed April 1, 1968 3 o Vv/ 7 0 LLLIE wmDmwmmm mi -P2300 mmmSZIO ZOrrmDmEOQ INVENTOR KURT ZENKNER June 6, 1972 K. ZENKNER 3,667,893

on. OR GAS BURNER WITH A CROSS-CURRENT BLOWER HAVING RETURN FLOW MEANS Filed April 1, 1968 5 Shanta-Shut 3 INVENTOR KURT ZGNK/VER June 6, 1972 K. ZENKNER 3,667,893

OIL on GAS BURNER WITH A CROSS-CURRENT BLOWER' HAVING RETURN FLOW MEANS Filed April 1, 1968 5 Shasta-Shut &

Fig. 6

INVENTOR ,Kum" Z NKNER June 6, 1972 k. ZENKNER 3,667,893

OIL OR GAS BURNER WITH A CROSS-CURRENT BLOWER 5 Shah-Shut. 5

HAVING RETURN FLOW MEANS Filed April 1, 1968 Highly Stable APSf Pressure 77 Pressure Fluctutions Workmg POIM A Psi Pressure Working point with equdl mixture speed at the baffle plate g INVENTOR KUKT ZENKNEK BY dW %%@Q-Y United States Patent 3,667,893 OIL OR GAS BURNER WITH A CROSS-CURRENT BLOWER HAVING RETURN FLOW MEANS Kurt Zenkuer, Hertzstrasse 12, Ettlingen, Germany Filed Apr. 1, 1968, Ser. No. 717,698 Claims priority, application Germany, Mar. 31, 1967, Z 12,777 The portion of the term of the patent subsequent to Aug. 27, 1985, has been disclaimed Int. Cl. F2311 /08 US. Cl. 431-79 35 Claims ABSTRACT OF THE DISCLOSURE An oil or gas burner has a casing formed by a lower casing member and a cover plate forming an elongated casing with rounded ends. A blower rotor is located in an opening in one of the ends, the casing wall adjacent the opening forming a guide plate at the intake side of the rotor. The angle between the tangent to the casing wall at the beginning of the guide plate and the tangent to the casing wall at the other end of the rounded end portion is less than 90, preferably 3060. There is provided at the other side of the rotor from the guide plate, where the rotor is slightly spaced from the longitudinal wall of the casing, a vortex bafile-plate which tapers in cross-section towards the periphery of the rotor, and between which and the end portion of the longitudinal wall one or more passages are formed through which some of the air fed by the rotor can be returned from the pressure-side to the suction-side.

BACKGROUND OF THE INVENTION (1) Field of the invention The invention relates to an oil or gas burner equipped with a blower to convey the combustion-air, said blower being designed as a cross-current blower.

(2) The prior art Known oil or gas burners of the type here in question have conventional blowers, such as axial or radial fans, or drum rotors, in order to convey the combustion-air to the mixing-chamber. As these blowers have a flat characteristic, the volume of air conveyed decreases as the back-pressure increases. For this reason, when such a burner is built into a heat-exchanger, there must be a measure of adaptation to the pressure-conditions of the relevant system, especially in that appropriate throttleunits are shifted and altered at the blower intake. This, however, can only be undertaken by experienced specialists and, in addition, relatively complex manipulations are required. Apart from this, note should be taken, in the case of such devices, that the systems pressure-conditions can change from day to day, as a result of the effects of the outside world, of the atmosphere, because of wind, and so on. For instance, variations in flue draught brought about by day-to-day conditions must be taken into account. In such cases the amount of air conveyed by the burners blower no longer corresponds to the amount of air needed, in relation to the set oilor gasconsumption, for good combustion. Such alterations in the fuel/air ratio can lead to sooting-up of the burner. Besides, in conventional blower burners the ignition process is particularly difficult, that is the volume of gas in the furnace-chamber expands very intensely and suddenly as a result of the sudden heat-development. Because of the fact that this increase in volume cannot drop quickly enough by escaping through the exhaust side, an aboveaverage high pressure builds up in the furnace-chamber,

3,667,893 Patented June 6, 1972 which can lead to pulsation of the burner, or even to blow-back of the flame through the burner.

SUMMARY OF THE INVENTION The invention purposes to avoid the above draw-backs to a great extent.

In achievement of the purpose proposed, and according to the invention, the new burner is provided with a socalled aerodynamically stable cross-current blower with a steep starting characteristic and a high final peak, for conveyance of the combustion-air to the mixing and combustion chamber. The new burner is therefore characterised according to the invention in that the blowers guideplate diverges constantly from the rotors cascade and passes into a spiral shape, in that the angle between the tangent at the start of the guide-plate, or the tangent at the turning-point on the inlet side, and the tangent to the part of the guide-plate wall limiting the outlet-region, is considerably less than degrees, preferably coming to between 30 and 60 degrees, in that the vortex bafiie-plate of the blower consists of two arms which together form an angle of about 10 to 60 degrees, in that the slot between the arm of the vortex baffle-plate on the suction side and the rotors cascade tapers towards the vortex, and opposite to the direction of rotation, and in that flow guidance means are associated with the rotor wheel, contributing to the formation of at least one return channel tapering from the pressure-side towards the suction-side, through which part of the air-current issuing from the rotor is returned from the pressureto the suction-side. Thus the vortex bafile-plate is preferably associated with the blowers rotor, and arranged opposite it, in such a way that the sucked air, on meeting the rotor in the region of the said baffle-plate, is directed more or less tangetially to the outer circumference of the rotor. The vortex bafile-plate can be made either wedgeor sickel-shaped, and can be movable and/or pivotable. In such an arrangement, an alteration of the back-pressure to a certain degree is not, as is the case in conventional blowers, linked to an intense alteration in volume, so that, to this extent, there is no necessity for adaptation to the prevailing conditions by specialists. The exact mixture-ratio of fuel to air can now be set by a specialists. The exact mixture-ratio of fuel to air can now be set by a specialist during manufacture of the burner without the need for subsequent adaptation to the pressure-conditions prevailing in the system for which the burner is used. Moreover, only one auxiliary operative is needed to adapt the burner to different combustion-chambers with the most varied pressure-conditions. The high final peak of the blower characteristicnothing comparable is found among the characteristics of conventional blowers--oifers an ideal opportunity to avoid pulsations on Warming-up, or even a blow-back of the ignition-flame. Apart from these advantages arising from the blowers characteristic, the described ultra-stable cross-current blower achieves a multiple of the pressure generated by conventional blowers of the same constructive size. Thus it is possible, with the same constructive size, to overcome considerably greater combustion-chamber resistance, than is today possible; it is also permissible to increase the pressure-drop in the mixer-device in the burner-head, which is reflected in improved combustion. However, the volume of air conveyed can no longer be altered by the changing and adjustment of throttle-units, which would remove the steep nature of the characteristic. According to the invention, flow guidance means are associated with the runner in this case, the said means contributing to the formation of at least one return-channel tapering at the pressure-side towards the suction-side, a greater or lesser part of the air current issuing from the rotor being led back from the pressureto the suction-side by the said channel. In this arrangement the characteristic retains its steep nature, and merely shifts linearly. As, however, these aerodynamically ultra-stable cross-current blowers react sensitively to units built into the area close behind the blower, as could happen, for example, on the introduction of the oil-jet body and of the igniter-electrodes, the burner-body with jet and igniter-electrodes is only built in behind an air-deflector. In this instance, the burner-tube preferably runs axially parallel to the blower-wheel. Here the combustion-air is led at right angled over guide-plates, or spirally into the burner-tube. By means of the guide-plates arranged in the spiral, a greater or lesser swirl of the flow can be maintained or avoided in the burner-tube. This type of air-deflection causes only small losses in flow, and guarantees uniform velocity distribution in the burnertube.

BRIEF DESCRIPTION OF THE DRAWINGS Exemplary embodiments of the subject-matter of the invention are shown in the drawing. Shown are:

FIG. 1, a diagrammatic side elevation of a burner according to the invention, in vertical section;

FIG. 2, a plan view of the arrangement as in FIG. 1;

FIG. 3, a perspective view of the arrangement as in FIGS. 1 and 2;

FIG. 4, a side elevation, in vertical section, on a larger scale, of the burner-head of the arrangement according to the invention;

FIGS. 40:, 4b, 40, various details of difierent embodiments of the burner according to the invention, each in side elevation, in section, and on a larger scale;

FIGS. 5, 6, 7, three diagrammatic views of variants of the blower to be used in conjunction with the burner according to the invention;

FIG. 8, a diagrammatic view of a further detail of the burner according to the invention, and

FIGS. 9, l0, and 11, three diagrammatic, pictorial comparisons of the burner according to the invention, with known burners.

FIG. 12, a cross-section through a modified form of bafiie plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The burner according to the invention has a casing consisting of a lower part 1 and a cover-plate 2. These parts can be pulled apart and thrust together. The coverplate carries the drive-motor 3, with pump 4 and burnerhead assembly 5, as well as all electrical parts, such as the magnetic valve 6, and so on. The lower part of the casing carries the burner-tube 7 associated with the burner-head assembly 5, and, along with cover-plate 2, encloses the blower rotor 8. The burner-head assembly, which is withdrawably inserted in the cover-plate, and which can be connected to it bayonet-fashion, carries on the one hand the burner-jet with the oil feed-pipe 11 and, on the other hand, the igniter-electrode 12 and the photocell 13 which serves to control the flame, the oil feed-pipe at the burner-head assembly being mounted so as to be movable to and fro longitudinally along the tube in the direction of arrow a, and the bathe-plate 14, in the direction of arrow 11, is mounted so as to be movable to and fro along the longitudinal direction of the oil feed-pipe. Guide-vanes 15 are also provided, associated with the blowers rotor for air-conveyance. The burner tube is attached on an annular flange 16 coaxial to the burner-head assembly, on the side of the lowercasing facing away from the cover-plate, in the region of guide-vanes 15, the said flange being bent outwards from the lower casing,

so that the transition between the inner surfaces of the lower casing and the burner-head assembly is well rounded-olf as an inlet, as shown at 18. The wall-parts of the lower casing lying opposite the frontal sides of the blowers rotor, and the cover-plate, offset from the other parts of the corresponding wall-parts, as shown at 20, 21, and a labyrinthine seal is provided between the frontal rims of the part of the base of the rotor associated with the vanes, and the corresponding parts of the casing wall. This labyrinth-like seal is particularly important in blower rotors whose length is less than their diameter; the said seal is designed as a labyrinth slot between rotor and blower, being radially less than 1% and axially less than 1.5% of the blower diameter. In the arrangement as in FIG. 4b, several, for example two, annular grooves 25 are provided in the casing-wall opposite the base 26 of the blower-wheel; these grooves are concentric, while in the arrangement as in FIG. 40, an annular groove 27 is provided in the casing wall, and an annular projection 28, fitting into the groove is provided in the base 29 of the blower-wheel. In both cases slot 30 or 31 is correspondingly restricted in size between the circumferential rim of base 26 or 29 and the opposed well-part 26a, 29a of the casing.

This results in a casing with a longitudinally-extended fiat prismatic shape (shown in FIGS. 2 and 3) both of whose axial end have generally flat substantially cylindrical sections demarcated by the circular areas 32, 33 occupied by the rotating members 5 and 8. These cylindrical sections, a jacket of one of which is formed by the blowers rotor guide-plate 51, are joined by the interior of a longitudinally-extended casing, 34, whose outline is formed on one longitudinal side by a partly curved wall 35 enclosing both semicircles at the axial ends. On the other longitudinal side, recesses 36, 37 are provided between both cylinders, 32, 33; between these recesses is a flap 38, bent upwards for uncovering the inlet for the blown air.

In the arrangement according to the invention the burner-tube with the jet-body and the igniter electrodes is mounted behind an air arrangement. In this instance the burner-tube is preferably parallel to the axis of the blower wheel. The combustion-air is then led at right angles over guide-plates, or spirally into the burner-tube. By means of the shape of the guide-plates mounted in the spiral, a larger or smaller swirl in the flow can be maintained, or avoided. This type of deflection causes only restricted flow-losses, and guarantees uniform velocity distribution in the burner-tube.

A further noteworthy feature of the subject-matter of the invention is that the lower casing can be formed with a spiral of any optional height (dependent on the maximum throughput) and that the lower casing is equipped with all the components, so that, in a very simple way (raised flap 38) absolutely perfect air-guidance is achieved. The burner-head assembly can be withdrawn, as by means of a bayonet closure. Very short, and also very long burner-tubes are feasible. The parts can be covered by the removable cap 40.

The lower casing, moreover, can be made by casting or injection, and the vanes can be cast along with it. The cover-plate can be made in a very simple fashion. The flange 40" is for attachment to the boiled wall 40a.

The cross-current blower of the burner according to the invention has a rotor 50, a guide-plate 51 guiding the air-flow, and a vortex bathe-plate 52 separating the ingoing and outgoing flow. The guide-plate diverges towards inlet 53, constantly away from the periphery of the rotor, and transmutes into a spiral shape. The angle at between the tangent 54 at the start of the guide-plate, or at the turning-point on the inlet-side, and the tangent 55 at the part of the guide-plate limiting the outlet-area is, according to the invention, considerably smaller than degrees, and preferably comes to 30 to 60 degrees. The vortex battle-plate 52 has two side faces 52a, 52b, together forming an angle of about 10 to 60 degrees. Finally, the arrangement is so designed that the slot 77 between the suction-side arm 52b of the vortex baffieplate and the periphery of the rotor tapers inwardly in the direction of the vortex, against the direction of rotation. Further, the arrangement is so designed that the sector angle 8 between diameter d which passes through the turning-point at the inlet-side, or the beginning of the guide-plate, and diameter d which passes through the point on the rotors circumference lying closest to the vortex baflle-plate, is less than 180 degrees. The sector angle 'ymeasured in the direction of rotation, or the opposite waybetween diameters al and d which passes through the point of tangency of the vortex bafl'leplate, lies between 5 and 60 degrees. It will be noted that the arrangement according to the invention is so designed that the air meeting the rotor in the region of the vortex bafile-plate is directed more or less tangentially to rotors circumference. This is attributable to the .11- rangement of the vortex bathe-plate opposite the rotor, and to its association with it. Another factor contributing to the effect according to the invention is that the area of the vortex baflle-plate lying closest to the rotor covers only a small section of the rotors circumference.

According to the invention, flow guidance means are associated with the rotor, said means contributing to the formation of at least one return-channel 75, tapering, for example, from the pressure-side 76 towards the suctionside 77, by means of which part of the air-current issuing from the rotor is returned from the pressureto the suction-side. In the embodiment in FIG. 5, the returnchannel 75 is formed by a small guide-plate 56 which runs at a distance from the vortex battle-plate. The flow shown in FIG. 5 is then created. Several return-channels, as in FIG. 7, can be made, to which end a series of successive guide-plates 57a, 57b, 570 are provided, together forming a wedge-shape, and making return-channels with the vortex baffle-plate 58. In all these cases the return-flow channel can taper from the pressuretowards the suctionside. A pusher can be provided at the inlet-opening of the return-channel. The guide-plates can, as in FIG. 7, be pivotable at the end nearest the rotor, towards and away from the said rotor. The vortex bafile-plate itself can also be formed as a means of flow-guideance, consisting of a hollow body, whose walls, on the pressureand suction-side, have holes, slits or like openings 78 (FIG. 12) to allow the medium to pass through. As in FIG. 5 at 52, and in FIG. 7 at 58, the vortex baffle-plate can have, in cross-section the shape of a triangular wedge, which, for example as in FIG. 5, can be pivoted around an axis parallel to the blowers rotary axis. However, the vortex baffle-plate can also be sickle-shaped (cf. 59 in FIG. 6), and, for example, can be movable along the rotors circumference while remaining parallel to itself, or it can be both movable and pivotable.

As in FIG. 8, a pivotable vortex baflle-plate can be linked to an indicator 60, which is pivotable along a scale 61 so that the air throughput can be exactly set. Up to a certain back-pressure, the volume of blown air is dependent on the said back-pressure. Pressure-fluctuations in the system have no effect on the set volume of air blow in. Variations in altitude, that is, whether the burner is used at sea-level or in the mountains, a fact noticeable in the air-density can be allowed for; likewise extreme combustion-chamber pressure.

-At 70, FIG. 9 shows the characteristic of an ultrastable blower, and at 71 the characteristic of a conventional blower. The ultra-stable blower is characterized by minimal volume-change on pressure-alteration; the etfective work-point can lie at a considerably higher pressure, with the same volume (better combustion). In FIG. 10 it should be noted, in the case of the usual blower with characteristic 72, the pressure in the combustion-chamber during the ignition process can momentarily reach a multiple of the working-pressure, exceeding the maximum pressure attainable by the blower, so that the flame blows back; this is not the case for the ultra-stable cross-current blower. FIG. 11 shows that, in the case of the ultrastable cross-current blower according to the invention, wedge-movement achieves a shift in characteristic, giving rise to a large and proportional regulable area, whereby even at the minimum setting a minimum volume is always blown. With conventional blowers, the throttle-unit causes high pressure-losses, and accurate setting is scarcely possible, as the forces at the start are too weak, and are later too strong, so that the regulable area must be judged to be small. In the ultra-stable cross-current blower, the amount of air blown increases in linear proportion to the wheel breadth, so that, at a given wheel diameter, the maximum volume can be determined by the rotor breadth. With known blowers, on the other hand, the blown volume cannot be achieved by enlargement of the blower width.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim is:

1. Oil or gas burner including a casing containing a blower to convey the combustion air, said blower being formed as a cross-current blower, wherein the blower has a rotor and the casing includes a guide-plate which diverges constantly from the periphery of the rotor in the direction away from the inlet and transmutes into a spiral shape, wherein the angle between the tangent at the beginning of the curvature of the guide-plate and the tangent to the section of the guide-plate limiting the outlet-area is considerably less than degrees, wherein the vortex bafile-plate of the blower comprises two side walls together forming an angle of about 10 to 60 degrees, wherein the slot between the side wall of the vortex baflleplate on the suction-side and the periphery of the rotor tapers towards the vortex and against the direction of rotation, and wherein the casing includes flow guidance means associated with the rotor, said flow guidance means contributing to the formation of at least one return channel means, tapering between the pressure-side and the suction-side, part of the air-flow issuing from the rotor being returned from the pressureto the suction-side by the said return channels means, means for feeding fuel into the path of air driven by the blower, and means for igniting the fuel-air mixture.

2. Oil or gas burner as claimed in claim !1, wherein the vortex baffie-plate is mounted opposite the rotor and includes means to direct the sucked-in air substantially tangentially to the rotors outer circumference.

3. Oil or gas burner as claimed in claim 1, wherein the vortex bafile-plate is mounted opposite the rotor and covers only a small section of the rotors circumference.

4. Oil or gas burner as claimed in claim -1, wherein the return channel means tapers from the pressure-side towards the suction-side.

5. Oil or gas burner as claimed in claim 1, wherein the return channel is formed between a small guide-plate set at a distance from the vortex hafile-plate and the part of the vortex battle-plate facing away from the pressureside.

6. Oil or gas burner as claimed in claim 5, wherein the flow-guidance means comprises several successive guide-plates, forming a wedge, said guide-plates, with the vortex bafile-plate, forming several return channels.

7. Oil or gas burner as claimed in claim 6, wherein the guide-plates are pivotable towards and away from the runner, at their ends nearest the runner.

8. Oil or gas burner as claimed in claim 1, wherein an adjusting-member is provided by adjustment of which the cross-sectional opening of the return-channel can be altered.

9. Oil or gas burner as claimed in claim 1, wherein a part of the vortex battle-plate constitutes the flow-guidance means, said bafile-plate comprising a hollow body whose walls have, on the suction and pressure sides, openings to allow the medium to pass through.

10. Oil or gas burner as claimed in claim 1, wherein the vortex bathe-plate has the shape of a wedge which is triangular in cross-section.

11. Oil or gas burner as claimed in claim 1, wherein the vortex battle-plate is sickle-shaped.

'12. Oil or gas burner as claimed in claim 10, wherein the vortex bathe-plate is pivotable around an axis parallel to the rotor axis.

-13. Oil or gas burner as claimed in claim 10, wherein the vortex bathe-plate is movable, while remaining parallel to itself, along the rotors circumference.

14. Oil or gas burner as claimed in claim 10, wherein the vortex bathe-plate is pivotable around an axis parallel to the blowers rotary axis, and is movable, while remaining parallel to itself, along the rotors circumference.

15. Oil or gas burner as claimed in claim 1, wherein the sector angle, directed towards the blowers suction side, between the diameter running through the beginning of the guide-plate, and the diameter passing through the point on the rotors circumference lying closest to the vortex bafiie-plate, is less than 180 degrees.

16. Oil or gas burner as claimed in claim 1, wherein the sector angle between the diameter passing through the beginning of the guide-plate and the diameter passing through the point of the vortex bafiie-plate, lies between and 60 degrees.

17. Oil or gas burner as claimed in claim 1, wherein the casing comprises two separable parts which can be placed together, namely a lower casing member and a cover-plate, in which the fuel feed means comprise a drive-motor with a pump and a burner-head assembly carried by the cover-plate and a burner-tube associated with the burner-head assembly carried by the lower casing mamber, and in which, inside the casing between the cover-plate and the lower casing, there is located the blower rotor.

18. Oil or gas burner as claimed in claim 17, wherein the burner-head assembly is withdrawably inserted into the cover-plate and contains a burner-jet with an oil feedpipe, an igniter electrode and a photocell for flame supervrsron.

19. Oil or gas burner as claimed in claim 17, wherein the rotary axis of the rotor and the longitudinal medial axis of the burner-head assembly run parallel to each other.

20. Oil or gas burner as claimed in claim 17, wherein the lower casing member and the air-guidance system are cast in one piece.

21. Oil or gas burner as claimed in claim :18, wherein the oil feed-pipe is movable to and fro longitudinally on the burner-head assembly.

22. Oil or gas burner as claimed in claim 18, wherein a baffle-plate is movable to and fro longitudinally along the oil feed-pipe.

23. Oil or gas burner as claimed in claim 17, wherein a burner tube is centered and fixed on an annular flange with the burner-head assembly, on the side of the lower casing member facing away from the cover-plate, the said flange diverging outwards from the lower casing so that the transition between the inner surface of the lower casing and that of the burner-head assembly is roundedoff.

24. Oil or gas burner as claimed in claim 17, wherein the sections of the lower casing member and the coverplate facing the rotor and lying opposite the frontal sides of the rotor are offset away from the rotor in comparison to the other sections of the corresponding wall-parts, so that the rotor contained between two opposed recesses in the casing wall, and in which a labyrinth-like sealingdevice is provided between the rotor vanes and the corresponding parts of the casing wall.

25. Oil or gas burner as claimed in claim 24, in which the rotor has a length less than its diameter, wherein the circumferential edge of the rotor lies only at a short distance from the facing surface of the casing wall, and

the parts of the casing wall lying opposite the rotors rims have several closely spaced concentric annular grooves of substantially identical depth.

26. Oil or gas burner as claimed in claim 24, in which the rotor has a length less than its diameter, wherein the circumferential edge of the rotors base lies at only a short distance from the facing surface of the casing wall, and the sections of the casing wall lying opposite the frontal edges of the rotor have a narrow annular groove in which an annular projection on the facing side of the rotors base revolves.

27. Oil or gas burner as claimed in claim 25, wherein the thickness of the groove is radially less than 1%, and axially less than 1.5%, of the blower diameter.

28. Oil or gas burner as claimed in claim 17, wherein the lower casing member has on its underside a flat wallpart, and has, along its circumference, a lateral limiting wall substantially at right angles to the said wall-part on the underside, the area of the said limiting wall lying opposite the blower inlet being bent upwards as a flap.

29. Oil or gas burner as claimed in claim 28, wherein the outline of the lower casing member corresponds to a longitudinal body which has on its two axial ends, repectively, a semi-circular form open towards the interior, and the two semi-circular forms of which are connected on the longitudinal side by an enveloping curve whereas on the opposite longitudinal side there are provided two constrictions and between these constrictions a tongue bent in upward direction.

30. Oil or gas burner as claimed in claim 17, wherein the casing has a longitudinal shape and the form of a flat prismatic body.

31. Oil or gas burner as claimed in claim 30, wherein the axial end portions of the longitudinal body constituting the casing have the shape of a flat cylinder, one cylinder mantle being constituted by a guide plate cooperating with the rotor of the blower, the said axial end portions of the casing having parallel longitudinal axes and being connected by a longitudinal casing having the shape of a fiat prismatic body, which on one longitudinal side has an opening serving as an air inlet and contains the vortex bathe-plate cooperating with the rotor of the blower and arranged between this rotor and the burner head, and further contains the guide elements for the air.

32. Oil or gas burner as claimed in claim 17, wherein the vortex baflle-plate is rotatably arranged on the casing and is connected with an indicator pivotably mounted on the upper side of the casing, which indicator is displaceable along a scale.

33. Oil or gas burner as claimed in claim 32, wherein for adaption to the height and/or the counter pressure the scale allotted to the said indicator is pivotable along a further scale.

34. Oil or gas burner as claimed in claim 17, wherein there is removable mounted on the cover plate a casing cap which serves to protect the elements carried by the cover plate.

35. Oil or gas burner as claimed in claim 17, wherein the burner-head, seen in the direction of air-flow, is mounted behind a means for deflecting the air.

References Cited UNITED STATES PATENTS 2,433,317 12/ 1947 Carter 431-265 3,079,981 3/1963 Loebel et a1 431--265 X 3,306,336 2/1967 Zenkner 230-425 X 3,398,882 8/1968 Zenkner 4l5--54 FREDERICK L. MATTESON, IR, Primary Examiner T. W. STREULER, Assstant Examiner US. Cl. X.R. 

